JPS5891544A - Reader for television signal recording carrier - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention stores television reading information in the form of a track, and each area and intermediate area of the track has a different effect on the irradiated light, and also transmits other information in the track reading direction. The present invention relates to a device for reading record carriers for television signals stored as undulations of tracks in the transverse direction.

In the case of color television signals, "other information" refers to color and sound information, which may be modulated onto 1, 8 or 4 carrier waves. In the simplest case, the television signal is a black-white signal, and the sound is modulated onto a single carrier wave. The track-like information organization can consist of a spiral track extending over the entire rotational range of the record carrier, or it can consist of a number of concentric tracks.

It is a disc-shaped record carrier in which all the luminance information as well as the color and sound information are recorded in one optical K1m capable track in a two-code system. The information track consists of a number of depressions or bits pressed into the surface of the record carrier. Luminance information is recorded by the spatial frequency of these depressions, and color and sound information are recorded by changes in the length of the depressions.
(so-called impact coefficient modulation).

When recording on a known record carrier, the intensity of the recording light beam is modulated, for example, by a photoelectric converter 81IWh, and a rectangular wave signal corresponding to the sound information to be recorded is applied to this light beam. When electronically synthesizing square wave signals from luminance information and color and sound information, it is necessary to limit the signal to produce high harmonics. If all the information is included in the fixed length area and the intermediate area, the carrier wave of the chain 1 being read will be confused with another carrier wave, which is not preferable. If a confusion component occurs in a frequency band covered by a modulated carrier wave, interference, a new moiré, will occur in the luminance information.Similarly, in a frequency band covered by another modulated carrier wave. When a confusing component appears, interference occurs in the color signal.

- When transmitting television signals via a carrier,
In order to minimize the appearance of confusion components between the bright station information and other information, it is preferable that the bone carrier for Television No. 1 has the above-mentioned configuration. When reading this i-sound information, the information contained in the 9-interval dark wave number of the area can be detected separately from the information contained in the undulations of the track. Therefore, there is little interaction between pieces of information. Such a record carrier also allows the transmission of television signals to take place in three separate systems.

In this case, an advantage can be expected that the frequency bands and stored signals do not overlap with each other.

The present invention proposes a reading device for this kind of Fa carrier, and therefore, the reading device for television signal recording of the present invention comprises:
comprising a light source and an objective lens system for supplying a light beam from the light source to a photosensitive information detection system via a record carrier, converting the light beam supplied by the light source and modulated by the area and the waviness into an electrical signal. The photosensitive information detection system is composed of four sensory detectors, and these detectors are arranged within the effective exit pupil of the objective lens system and are located in different quadrants of an X-Y coordinate system passing through the skeleton exit pupil. , the X-axis extends in the track reading direction, and the Y-axis extends transversely thereto, respectively, to form an i-image.

In a preferred embodiment of the record carrier reading device of the present invention, Ill and @S
The outputs of the detectors placed in the quadrants are connected to a first summation device and connected to the sum # of the output terminals of the detectors placed in the 1:Q and 11E4 quadrants. And wXl
and the summing device of the IEs is connected to a differential amplifier, and on the output side of the differential amplifier, the information of the other carrier wave recorded as the undulation is generated, and placed in the 11:1 and IIIL4 quadrants. Connect the output terminal of the detected detector to the summation device @8, and *S
and the output terminals of the detectors arranged in the fourth quadrant are respectively connected to a fourth summing device. Further, the eighth and fourth summation devices are connected to an amplifier so that the information recorded in the area is produced on the output side thereof.

Nao,) 'Itsu 131% Allowed 1: B, 84$1,90e1
In the issue, an optical information tissue reader with 4-1 detectors was proposed. However, in this device, the information detection system consists of only three detectors, and these detectors read the information contained in the spatial frequencies of the region. The other three detectors are used to measure the necessity of a reading spot for a track to be read.

The invention will be explained below with reference to the drawings.

Figure 1 diagrammatically shows a part of a disc-shaped record carrier in which a television signal, for example a color television signal, is stored.

A large number of tracks 2 and lands 8 are provided alternately on this record carrier. In the record carrier to be read by the apparatus of the invention, the tracks are undulated from their reference positions, as is clear from FIG. S, which shows a part of the tracks enlarged. The dashed line 6 shows the average position of the track center inherited over a large track length. In the track of FIG. 1, if it is helical, the corresponding lines 6 will be concentric or quasi-concentric. The local period of waviness is denoted by Ps. This period is determined by the color and sound information in the case of a chromatic television signal and therefore varies along the track. Tracks include multiple area numbers and intermediate! It consists of an alternating array of 5 regions.

The local 4 stages of these areas are indicated by Po. This period is determined by the luminance information of the color-corrected television signal. The period P is approximately eight times as long as the period P. In FIG. S, the waviness amplitude is exaggerated. In practice, this amplitude is smaller than the period in the transverse force direction of the track, for example 1/1/1 of this period.
It is lo.

The track structure in the Chiku1 diagram and the IIS diagram can be regarded as a two-dimensional grating that diffracts light used for reading in multiple directions. Since the diffraction caused by the track undulations occurs in different directions than the diffraction caused by the transition between the region and the intermediate region, the information contained in the undulations can be detected at the transition by employing an appropriate detector. Neutralization of the information contained can be read separately.

As shown in the IEs, the color and sound information can be replaced by the spatial frequency of the undulations. However, instead of this, color and sound information can be recorded by width modulation of the undulations at a constant period. Furthermore, the waviness of the track can be frequency modulated as well as amplitude modulated, so that color information can be recorded, for example, by the spatial frequency of the waviness, and sound information can be recorded by the amplitude of the waviness.

The information structure is preferably a phase structure, whereby the phase of the light follow-up beam is modified. The areas are for example arranged at a different depth within the record carrier than the intermediate areas and the lands. The record carrier can be a light reflector or a light transmitter. The geometric distance df between the region plane and the intermediate region plane to allow sufficient reading of this phase structure is such that the optical distance d0 is approximately (1
* + 1 ) b, where λ is the wavelength of the reading beam and n is an integer (n=0, 1, 1!
etc.). The optical distance d0 is given by (!0=N df, where N is the refractive power of the medium covering the region and the intermediate region.

By selecting such an optical distance, the part of the beam read from the record carrier that comes from the area has a smaller optical path (In+〇-
It passes through a long or short optical path.

In the case of a reflective type in which the phase structure is in contact with air (, N=1), there is.

Figure 1iEB shows an example of a device according to the invention for reading a reflective record carrier. The light flA11 is, for example, a laser light source, which emits a reading beam IB.

This beam is directed by the objective system shown diagrammatically with a single lens L0 into the information plane on the I5 brass carrier 1? Focus the light on top. In the figure the arrangement carrier is shown as a cross section. The track is indicated by B. The beam reflected by the record carrier and modulated by the information structure passes through the objective lens L0 at the Ifth point, and then passes through the semi-transparent mirror 1.
The light is reflected to a photosensitive information detection system 14 diagrammatically indicated by 8. Connect the output terminal of this detection system to the electronic circuit 19,
Within this circuit, the signals from the detector are added and subtracted in a special way. Decoding the resulting signal.

In the present invention, the detection system 14 is arranged within the plane of the effective exit pupil of the objective lens system L0. This objective lens system L0 is composed of several lenses. The actual exit pupil of such an objective can be located outside the objective or within the objective.

In the first case, the detection system is placed in the actual exit pupil, which therefore also forms the effective exit pupil. In the latter case, the detection system can be placed within the actual exit pupil, but it is necessary to form an effective exit pupil outside the objective lens system. This effective exit pupil is m
This is an image of the actual exit pupil formed by the field lens L, as shown in figure s. For clarity, this drawing shows only a' of line point a of the exit pupil. The effective exit pupil may also consist of one shaded image of the actual exit pupil.

FIG. 114 shows the detection system 14 seen from the side (as a cross section along lines 4/ and 4/ in FIG. 8). This detection system is composed of four photosensitive detectors 15, 16, 17, and 18. To indicate the relative position of these detectors to the track structure,
A protrusion 3' of the track to be read is drawn on the information detection system.

By rotating the record carrier 1 around the axis 80 and simultaneously moving the optical reading system and the arrangement carrier relative to each other in the radial direction,
The signal representing storage information is detected by detector 15.16.1? and 1
8 output terminals.

FIG. 5 shows the processing means of item 1 above. detector lb and 1
The output signal of 6 is sent to the summation device f120 and also to the detectors 17 and 1.
The output signals of 8 are fed to a summation device B1. From these summing devices the signals are fed to a differential amplifier S4, which produces a signal 8r relating to the information contained in the deflection of the output lateral pressure track. The information contained in the various spatial frequencies of the region is collected by a summation device 1111. It is reproduced by supplying the output signal of ilB. The input terminals of these summation devices are respectively connected to detectors 15.18 and i6. l? The output terminal is connected to the differential amplifier 15, and the differential amplifier O generates a signal.

Next, the reading principle will be explained with reference to FIGS. 6 to 11 and IE18 to IE15.

If the lens L has no aberrations, it will form an accurate radius B in the plane of an object V placed in the object plane V (see diagram !lEa). Information about the object transmitted through the lens exists in a beam cross section within a plane perpendicular to the optical axis at any point on the optical axis oo'-H. However, in practice, information forming the exit pupil plane of the lens L is detected and this information is rarely observed separately from other information in the image plane.

When the object is a lattice, the light beam C is split from K into a zero-order and one-order beam Co, three first-order and one-order beams C+1 and C-0, and a large number of higher-order beams (not shown). The zero-order beam itself has no information about the object; this information is distributed to other systems. If the pupil of the lens is large enough, the complete grid will produce an accurate image of the lattice in the Km plane. It is not possible to distinguish individual beams within sight.

However, these beams can be somewhat distinguished within the plane U of the exit pupil. Figure 7 shows the weight of the boxes.

In Figure 7, circle 80 indicates the exit pupil, circles 81 and 8!
1 indicates the cross sections at the exit pupil position of the +1st-order beam and the -1st-order beam, respectively. The positions of circles 81 and 8s relative to the center of circle 80 in the plane of the exit pupil are determined by the period of the grating. It is known from the general theory of diffraction gratings that gin α of the angle α formed between the principal ray of the −th order beam and the principal ray of the zeroth order beam is proportional to λ/2. Here p
Let λ be the grating period and λ be the wavelength of the beam C.

As the grating period decreases, the diffraction angle α becomes (circles 81' and 8
8') increases.

As the grating period increases, the +1st order and -1st order beams gradually overlap. Individual detectors (II? 88 and 84 in the figure)
-Q) is placed in the left and right halves of the exit pupil.
The +1st order and -1st order beams can be considered to be detected by measuring their influence on the zero order beam. but,
This lattice has special properties consisting of: First of all, the IIEIK track is not straight, but has undulations. Furthermore 1. The tracks are not continuous tracks, but are a combination of discontinuous ranges. Finally, the track is moved relative to the objective lens system. The undulating track-like information structure, which is a combination of discrete regions, directs the light used for reading in a number of different directions depending on the stored information. The effect of continuous track waviness on the read beam will be explained next.

FIG. 8 shows a portion of a continuous track S'. This track is illuminated by the reading spot of the sensor 8.

During reading, the reading spot and the information track move relative to each other in the direction of arrow 5s. During this time, the reading spot 8 and the exit pupil of the objective lens are always centered on the dotted line 61 hK. This dotted line shows the average amount of snow at the center of the track. truck 5
Due to the torsion, the particles are diffracted in the directions indicated by the 4IK arrows pkqer and 8. The beams diffracted in these directions are superimposed to read out the information recorded by the undulations.

Figure @9 shows the state of the diffracted beam in the diagonal direction on the exit pupil plane. The central circle 68 reduces the exit pupil size. 8th
It was diffracted in the directions of peqyr and 8 in the figure (-11+
1 ) + (+1 t −i ) +(+ l g
+1) Cross sections at the exit pupil positions of the m and (-is-i) order beams are represented by circles 54, 55 degrees s6 and 67. The centers of these circles are p' and q'.

Let r' and B' have the same radius as the circle 58.

The distance e in 1I98OK is expressed as a function of λ/pT, where p is the period of the track structure in the direction transverse to the reading direction 6a. This period can be considered constant. The distance f in FIG. 9 is a function of λ/15i, and pi represents the period of waviness in the reading direction.

As shown in Figure 9, the detectors 15 to 18 are arranged in the region where the primary sub-beam overlaps the zero-order beam.

interfere with The intensity of the light in these regions depends on the phase of the first order sub-beam relative to the phase of the zero order sub-beam. When moving the track with a waviness relative to the reading beam, the phase of the primary sub-beam changes. This change can be seen in Figure IIE10a and IE10a by displaying the phase.
lOb5! It can be represented by a phase vector as shown in the J+IE10c diagram and the llXlod diagram. Zero-order beam (
The electric field vector Woo of 0,0) rotates at a speed of -5'e together with the electric field vector of the primary beam. At a point on the track, the (-1, +1) order beam has a phase vector wo having an angle with respect to the vector l. (→1.-
1) The order beam has a phase vector ζ that makes the same angle with the vector gooK as the phase vector 〒. When the information track moves relative to the reading spot as shown in Fig. 8, the phase angle of the (+1.-1) order beam increases, and the (-1,
+1) The phase angle of the order beam decreases.

When reading an undulating track, the vectors i and 1 corresponding to these diffraction orders are therefore rotated in opposite directions. The vector ma and i are (+l e + 1
) and (-1, -1)-order beams.

These vectors also rotate in opposite directions during track reading. Because of the left-right symmetry, the directions of vectors 〒 and i are opposite to the directions of vectors i and i. Starting from the initial state of FIG. 10a, the reading spot moves in the reading direction by a distance corresponding to -4 of the partial waviness period,
The state is as shown in the 1tlOb diagram. Figure 11Oc shows the state when the reading spot has finished moving in the reading direction by a distance corresponding to half of the partial waviness period, and the 10th (Fig. When the reading spot has moved a distance corresponding to the partial waviness period, it returns to the state 11 in FIG. 10a.

The intensity of the region where the first-order sub-beam overlaps with the zero-order sub-beam is determined by the phase difference between these two beams, that is, the vector S e q e in the direction of the vector mouth, referring to Figure 1110.
It is proportional to the components of F and i.

The components of vector i and 〒 in the direction of vector i are O(m
lOa diagram) to negative limit value (see IE10b diagram) V
cll, becomes zero again (see IiEloc diagram), and then becomes a positive limit value (tI!, see 1od diagram). Also, the components of the vectors h and i in the direction of the vector mouth change in the opposite direction to the E notation, that is, from 0 to a positive limit value, then to zero again, and then to the eclipse limit value.

The (0,0)-order beam shown with diagonal lines in the Mto diagram and the (-1e+
l)I (+1.+1)# (+1.-1) and (
In the overlap region with the -1, -1,)-order beam, constructive interference and destructive interference alternately exist due to the phase change of the first-order beam relative to the zero-order beam. The light intensity alternately increases and decreases within the region.

The change in the undulation and therefore the change in light intensity determined by the stored information is detected by the photosensitive detector 1! i, 1t1゜17 and l
8 (See diagram IE9) Can be detected from K.

The light intensity changes resulting from diffraction in the p and r directions are in phase with each other, and these changes are in opposite phase to the light intensity changes resulting from diffraction in the q and 8 directions. The signals provided by detectors IIs and 16 are added together, and the signals provided by detectors 1f and 18 are also added together. Each summation signal exhibits a time variation corresponding to the spatial variation of the waviness of the track', but these summation signals are 180" out of phase with each other. By subtracting the summation signals from each other, a double amplitude information signal Sr is obtained. can get.

When reading the information recorded by the track waviness, instead of the S detectors 15 and 16, one detector having the same surface area as these detectors 916, 16 can be used. Is this idea detection/exit 81? and 18. However, four detectors can also be used to read the information contained in the inter-frequency frequencies of the region.

1119 Centers p / , q / , r / in figure
The positions of and a/ are determined by the period of the track waviness. As the spatial frequency of the information with the record 1 carrier increases, in other words as the local period of the waviness decreases, the center p'+
q'tr' and B' are the center circles! 18, the area of overlap between circle 58 and circles 6B, 66, and 67 decreases. Therefore, the primary B''-4 is the zero-order B1
, the more it interferes with Mu, the smaller Maro becomes. This is the record carrier E
If the spatial frequency of the information is high, then the detector 1! S, 16
．． 1? and 18&C, which means that the magnitude of the signal provided by 18&C is reduced.

When information, such as chrominance information and sound information, is recorded as a periodic representation of undulations as described above, the electrical signal S has a constant amplitude and its frequency changes. Note that information can also be recorded by the amplitude t' scale of the waviness. In this case, the period Pr is no longer considered constant; E9
Centers p/, q/, r/ and 8 in the figure
' moves down E alternately during reading of the record carrier. Figure 10a,
Regarding the vector diagrams in Figures 10b, 10c, and Jll'lOd, this means that the vector B
This means that e'q + F and the length of the dip change depending on the stored information, and the rotation speed of the vector relative to the vector Eoo is constant. Therefore, the electrical signal S
, has a constant frequency and a varying amplitude.

1110a, 1K10b, @10c and 10d
The figure is based on an initial state 1aK in which the angle between the vectors p*q*'F and i and the vector blue is 90". This is because the tracks of the information structure create a difference in optical path length in the reading beam. corresponds to the case, and this difference should be considerably smaller than a quarter of the wavelength of the wavelength used for the reading.There is an initial maximum shift in phase between the -order and zero-order beams, but the first-order vector The amplitude is extremely small compared to the zero-order beam amplitude,
In other words, speaking about the vector diagram, the phase vector 3゜i
, T and : are extremely small, and the change in optical intensity at the detector is extremely small. In practice, the most ideal situation is one in which the tracks produce an optical path length difference corresponding to -a quarter of the wavelength of the reading beam.

In order to obtain such an optical path length difference, in FIGS. 10a, 10b, 10cm, and 106, eight vectors among the phase vector; has an initial angle of 45° and other S
Let the vectors have an initial angle of 185°. However, for the reading method shown in Figure 111E6, i.e. the signals of detector 16.16 are added and
In the method of adding the signals, it is possible to change the optical path length difference over a fairly wide range around a quarter wavelength without reducing the amplitude of the detection signal too much. FIG. 13 shows the amplitude of the detection signal 81 as a function of the optical path length difference W caused by the undulating track. This means that the information contained in the undulations can be read sufficiently by summing them so that there is a difference in optical path length between a quarter wavelength and three-quarter wavelength. However, in the reading method described above, if the track causes an optical path length difference of approximately O or half a wavelength in the reading beam,
Unemployable.

Figures 11a and 11b show three phase vector diagrams corresponding to the last case. Figure 11a is! The initial state corresponding to the ElOa diagram is shown, and the 1E11k) diagram shows the state after the reading spot has moved on the track by a distance corresponding to a quarter of the waviness period. These local areas 1 show that the sum of the components of vectors 5 and 7 in the direction of the vector island varies slightly from the actual
This means that the signal obtained by adding together the output signals of 1 and 16 changes slightly. Also, the frequency of this total signal will be three times the frequency corresponding to the spatial frequency of the track waviness. The electrical signal supplied by the summation device IQ in the aS diagram is therefore a distorted signal of small amplitude. This is a total of $5 figure! l! The same is true for the electrical signal provided by fBx.

The truck! l[A signal carrier that causes a half-wavelength difference in optical path length in the beam can be read by signal processing using means other than the means shown in FIG. The signals from detectors 15 and 16 and from detectors 17 and 18 are then subtracted from each other. The difference signal is fed to a differential amplifier to obtain the information contained in the track waviness at its output.

However, the signal obtained by such summation is incomparable to the signal obtained by reproducing the information track structure which produces an optical path length difference of about a quarter wavelength by the signal processing means shown in FIG. 8N
The ratio is inferior.

Information is contained not only in the undulations of the track, but also in the spatial frequencies of the region. In FIG. 18, a straight track S'' is shown, and this track is composed of a region 1 and an intermediate region 5. This track is light.

Scanning is performed using 8 reading spots. At the transition between the zone and the intermediate zone the reading beam is reversibly diffracted in the k and 1 directions.

FIG. 14 shows the extent of the exit pupil plane of the objective lens system due to this diffraction. Circles 58 and 69 are (-
1, O) and (+1, O) order beam cross sections,
These beams are diffracted in the directions indicated by 1 and K in the IE1g diagram. Let the centers of the circles 158.69 be 1' and 2', the radius be the same as the radius of the circle lSa, and the circle Is8 indicate the exit pupil of the objective lens system.

The distance f is proportional to λ/pyK, where p is the period of the region.

! The E11Sa diagram shows the corresponding phase vector diagram for a special point in the track in the case where the region produces an optical path length difference of less than the reading beam neutralizing quarter wavelength. Vectors i and i make 90° with respect to vector i, and vector L indicates the electric field vector of the (o, o) order beam. When the reading spot moves in the direction of 5s with respect to the track and reads the information contained in the neutralized area, the phase angle of the beam diffracted to the right increases and the phase angle of the beam diffracted to the left decreases. do. This means that the vector k in the vector diagram
and 1 mean that they rotate in opposite directions with respect to the vector Woo. tjlL15b figure, *16c figure and! E
LB (Figure 1 shows the directions of vectors k and 1 at points separated by a distance corresponding to a quarter of the partial period of the domain structure. The components of vector e in the direction of vector Boo vary from 0 to the negative limit value. , and then becomes zero again, reaching the limit value at its end.The components of the vector i in the direction beside the vector change in the opposite direction, that is, from zero to the positive limit value,
Next, it becomes zero again and then changes to the limit value of eclipse. Therefore, (
+1.0) and (-1, 0> order beam phases change relative to the zero order beam phase 9, which means that 11E14
The (0.0)-order beam indicated by diagonal lines in the figure and (+l, O
) and the (-1, O)-order beams alternately perform constructive interference and destructive interference, meaning that the light intensity in these regions alternately increases and decreases. The changes in light intensity determined by the transitions between the zone numbers and intermediate zones can be detected by the same detectors 16, 16, 17 and 18 used to read the information contained in the undulations of the tracks. Light intensity If caused by diffraction in one direction
The phase change to f is opposite to the change in intensity due to diffraction in the k direction. The intensity changes in the positions # of detectors 16 and 17 caused by the (-1,0) diffraction-like lines are mutually equal, and the detection 1! caused by the (+1.0) diffraction-like ftm!
! The optical intensity change at 16.18 is also equal. The output signals of detectors 16 and 17 are added together (in the summing devices B1 and zB of Figure 6), and the output signals of detectors 15 and 18 are also added together. The sum signals thus obtained are subtracted from each other (in the differential amplifier S6 of FIG. 5) to obtain an electrical signal 8t, which contains the brightness information of the television signal.

IE16a diagram! E16b figure, 1st! Ic diagram and 1b
Figure d shows the initial node when the angle between vectors k and 1 and vector Woo is 90°. In this case, the regions produce optical path length differences in the reading beam that are considerably less than a quarter wavelength. However, in this case (+1.O) and (-1,0)
The amplitude of the next beam is much smaller than that of the zeroth order beam,
Regarding the vector diagram, the lengths of vectors k and l are smaller than vector Woo, and the change in light intensity at the detector is extremely small. In practice, therefore, we select a record carrier whose area produces an optical path length difference of -a length, which is a quarter of the internal pressure of the reading beam. 186 for vector i
It means forming an angle of °. Reading such a record carrier can be carried out by subtracting the sum signal of detectors 16 and 170 from the sum signal of detectors 16 and 18, and by adding both said sum signals. That is, in Figure 115, element 8B is a differential increase! It can be used as a width amplifier or as an addition amplifier. In this respect, the summed signals may be summed, since this summation allows a small spatial frequency of the reading area in the information structure.

Satisfactory reading of the information contained within the region can be obtained (with good 8N ratio) even if the region produces an optical path length difference in the reading beam other than a quarter wavelength. For example, information whose region produces an optical path length difference corresponding to half a wavelength cannot be read satisfactorily when the signals provided by three detectors placed in the left and right halves of the exit pupil are summed. I can do it.

The regions mutually form undulating tracks. The optical path length difference caused by the area is therefore determined by the optical path length difference caused by a continuous K (wavy) track, which track can be read accurately. The optical path length difference caused by the region therefore varies within the range of one wavelength of the section to three wavelengths of the section when the signals provided by the detectors 15-18 are processed by the means of FIG. 116. The above optical path length difference allows signals from detectors 15 and 16 to be detected mutually and! 1? and 18 can be half a wavelength if they are subtracted from each other. In the track part of Figure 8,
The period P of the undulation is eight times the period P of the area. When a track is composed of areas, a type of sampling of the track can be performed. According to this sampling theory, K should be at least li, 7 times the spatial frequency of the undulations in order to achieve satisfactory signal transmission. Furthermore, in order to prevent the uncertainty regarding the phase of the waviness from becoming too high, it is necessary to set an appropriate number of regions within the opening period of the waviness.

Furthermore, the (0.+1) and (0,-1) order beams diffracted in the X and X' directions perpendicular to the dotted line in FIG. 8 are excluded from the explanation. These beams do not carry any television information. However, these beams can be used to control the centering of the reading spot with respect to the track to be read. In this case, the centering error appears at a lower frequency than the frequency associated with track waviness determined by the television signal. This low-frequency component occurs in the electrical signals supplied by the upper and lower detectors, and by comparing these components a control signal is obtained for modifying the position of the reading spot relative to the track to be read. It will be done.

However, in the present invention, the centering error of the read spot can be detected by observing the high frequency waviness of the track instead.

In this case, a certain localized additional undulation is applied to the track,
This period is made longer than the average period of the waviness of the distribution high frequency. The additional waviness additionally modulates the detector position and its phase allows the centering of the read spot to be measured. A low frequency acid component is derived from the signal provided by detector a to correct the read spot centering in known manner. Did the applicant first develop the technique of centering using the undulations of the track in the Netherlands? , 814. This is a technology already proposed in gt17.

The information structure to be read by the device of the invention can be recorded on a record carrier by the device proposed earlier (in Dutch Patent Application No. 7,814,16?). In this device, f, ! of a photoelectric modulator, etc. IIIPIIL quality control device and Koon JR
gl14! ! A directional modulator such as II is provided in the optical path from the light source, and the recording light from the light source is supplied to the photosensitive surface of the record carrier. The photoelectric generator G* splits a single light beam into a number of light pulses of light intensity, and these light pulses record an area in a track. , Shion WaS is capable of recording tracks with undulations by changing the direction of the recording beam by a small angle in accordance with the signal supplied to the Ill'll device.

[Brief explanation of the drawing]

Figure 1 is a route map showing a part of the disc-shaped record carrier, Figure 8 is an enlarged partial view showing one track of the information structure to be read by the device fK of the present invention, and *Figure a is the television signal of the present invention. The system diagram of the recording carrier reading device, Figure 4 is the route map of its detection system, and the ms diagram is the plot diagram of the signal processing means in the device shown in Figure 8. - Figures 18 to 1b are the route diagrams of the reading mechanism; Figure 1S is a diagram showing the amplitude of the detection signal as a function of the optical path length difference caused by an undulating track; l... Recorded carrier, 2... Track, 8... Land, 6... Average position of the center of the track, ? ...Information plane, 11...Light source, lfi...Reading beam, 18...
- Semi-transparent mirror, 14...Detector, 15-18...Detector, 19...Electronic circuit, go, ms, s8...Summing device, 14.16...Differential amplifier. Patent applicant: NPA Philips Fluiran Pen 7 Abriken

Claims (1)

[Scope of Claims] L Television information is stored in the form of a track, and the regions and intermediate regions of the track each have a different effect on the irradiation beam, and other information is stored in the track in the transverse direction with respect to the track reading direction. A device for reading a record carrier for television signals stored as undulations, comprising a light source and an objective lens system for supplying a light beam from the light source via the record carrier to a photosensitive information detection system, the apparatus comprising: a light source supplied by the light source; The photosensitive information detection system that converts the light beam modulated by the area and the undulation into an electrical signal is composed of four photosensitive detectors, and these detectors are arranged within the effective exit aperture of the objective lens system. The positions I! in different quadrants of the X-Y coordinate system passing through the exit pupil! 1. A reading device for a record carrier for television signals, characterized in that the X-axis extends in the track reading direction, and the Y-wheels extend in the lateral direction. 1 Connect the output terminals of the detectors placed in the 11EI and Hina Z quadrants to the 11:1 summation device, and connect the output ° terminals of the detectors placed in the Chin 8 and Makiban quadrants to the third summation device. and connect the first and ml summing devices to a differential amplifier, and produce other information as the wave on the output side of the differential amplifier with ml and ml in the four quadrants. Connect the output terminals of the placed detectors to the 8th summation device, and connect the output terminals of the detectors placed in the S and @8 quadrants to the summation device of the block 4, respectively, and connect the $8 and the fourth summation devices. A reading device for a brass carrier for a television signal as claimed in claim GS, characterized in that the reading device is connected to an amplifier, and the information recorded in the area is generated on the output side of the amplifier.